Treatment of hydrocarbons



Patented May 5, 1936 UNITED STATES PATENT OFFICE TREATMENT OFHYDROCARBONS No Drawing.

4 Claims.

This invention relates more particularly to the treatment of hydrocarbonmixtures of motor fuel boiling range produced by polymerizing reactionsupon normally gaseous olefinic hydrocarbons.

In a more specific sense the invention has reference to a process forremoving undesirable reaction products from the hydrocarbon polymersproduced by the action of sulfuric acid upon normally gaseous olefinichydrocarbons of relatively low molecular weight.

Olefinic hydrocarbons, with the polymers of which the present inventionis concerned, occur along with corresponding paraffinic or saturatedhydrocarbons in commercial hydrocarbon gas mixtures such as thoseencountered in the cracking of petroleum. in gas making processes and asby-products in various chemical industries. In general they are morechemically active than other classes of hydrocarbons, particularly ifthey contain more than one double bond or triple bonds between carbonatoms. Even when under mild catalytic influence they exhibit thisreactivity in their pronounced tendency to polymerize and formsubstances of higher molecular weight. In most instances thisinstability is a disadvantage, particularly in the case of crackedhydrocarbon oil distillates which are of suitable boiling range topermit their use in internal combustlon engines, since the polymerswhich develop on storage are of a gummy character and impart color tothe oil.

Olefins occur in particularly large percentages in the fixed gases fromcracking processes as well as in the gasoline boiling range fractions.The fixed gases are utilized principally as fuel, only a very smallpercentage of present day commercial production being subjected toprocesses for the recovery or utilization of the olefinic constituents.The manufacture of secondary alcohols such as iso-propyl alcohol andothers by first absorbing the corresponding olefins in cracked gases insulfuric acid and then hydrolyzing the acid esters has been undertakento a limited extent. By suitable modification of conditions in regard tostrength of sulfuric acid, temperature, pressure, rate of flow andefficiency of contact, the lower molecular weight olefins in hydrocarbongas mixtures may be controllably polymerized to compounds correspondingto their dimers and trimers which in the case of normally 0 ctylene.Application December 4, 1933, Serial No. 700,878

Boiling points of olefin dimers 1o Polymers such as the above producedby the action of sulfuric acid as a catalyst are prone 20 to containconsiderable percentages of sulfuric acid esters, since ester formationis the primary reaction occurring between olefins and sulfuric acid. Inthe case of alcohol manufacture these esters are hydrolyzed, and in thecase of polymer 25 manufacture, while the major portion is decomposed,the amount of undecomposed esters may be considerable and it is with asimple and practical method of removing these esters that the presentinvention is concerned. 30

On one specific embodiment the invention comprises treatment ofsynthetic hydrocarbon mixtures of motor fuel boiling range, produced bypolymerizing olefins in the presence of sulfuric acid, with phosphoricacid to desulphurize them 35 and produce other refining effects. Theinvention further comprises the use of graded mixtures of sulfuric andphosphoric acids for the same purpose.

The following equation shows the reaction 4 which occurs betweenpropylene (representing an olefin) and sulfuric acid:

OH O H +H SO S F l- Mono-propyl ester e of sulfuric acid The compoundshown on the right of the equation I typifies a number of esters orsimilar structure which as previously stated may remain dissolved in aliquid hydrocarbon mixture produced by polymerizing reactions amongolefins in the presence of sulfuric acid.

According to the invention the'hydrocarbon liquid containing suchdissolved compounds is treated with phosphoric acid or the abovementioned graded mixtures of phosphoric and sulfuric acids, the courseof the main reactions being evidently somewhat as follows:

OH OH 0 03111 S0: +O=POH=H2SO4+O=POH 0 Q1111 OH OH Mono-propyl esterPhosphoric Mono-propyl ester of sulfuric acid acid of phosphoric acidThe compounds on the right hand side of the equation are evidentlysoluble in the phosphoric acid employed in the treatments, at least upto a high concentration since, as will be shown later, a large quantityof hydrocarbon mixture containing sulfuric acid esters may be treatedbefore the equilibrium is reversed and the treating efficiency of thephosphoric acid drops below an economical point.

The phosphoric acid esters remaining dissolved in the sludge phosphoricacid mixture after treatment may be hydrolyzed to produce alcohols, thefollowing equation representing the reaction between water and themono-iso-propyl phosphate shown above:

0 03131 OH O=P0H +H2O=O= P/'OH+CIH7OH OH OH Mono-propyl ester PhosphoricIso-propyl of phosphoric acid acid alcohol It will be obvious from theabove equation that the phosphoric acid is regenerated and merely needsconcentration by heating to bring it to a condition for further use.There are obviously some limits to this regenerating step since there 1are other compounds present which are of a less concentration. Howeve itis within the scopeof the invention to employ other acids of phosphorusinsofaras they may be applicable. Thus, when mixtures of sulfuric andphosphoric acids are employed. an acid of phosphorus containing lesswater in the molecule may be mixed with sulfuric acid to form a treatingreagent. Examples of such acids are pyrophosphoric acid andmetaphosphoric acid, the formulas of which are shown below along withsome of their commoner properties.

- Acids of phosphorus 11C. Dec. C.

Sublimes 38.6 Loses H10 The acids of phosphorus in which the phosphorushas its lower valence of 3 may also be used if desired but as a rulefind less ready application on account of their. relatively greater costand generally lower chemical and solvent action.

Treatments of hydrocarbon polymer mixtures according to the presentprocess may be conducted at ordinary or slightly elevated temperatures,say, of the order of 50 to 60 C. and opera.- tions may be conducted inany of the well known types of equipment used in treating low boilingdistillates with sulfuric acid, such as batch agitators and continuoustreating plants consisting of a series of mixers for the treatingreagent, including neutralizingliquors and water washes, each mixerbeing followed by a settling drum to permit settling and removal of thereaction products. The details of such operations are well known tothose conversant with refinery operations and need only be mentionedhere.

A specific example of the results obtainable by a treatment comprisedwithin the scope of the invention will be of assistance in showing itsvalue in connection with the treatment of hydrocarbon mixtures'producedby polymerizing reactions upon normally gaseous olefinic hydrocarbonscontaining sulfuric acid esters and other organic products of sulfuricacid treatment.

The polymer stock treated may have been produced as a result of treatingin the presence of sulfuric acid, an olefin-containing gas mixture froman oil cracking plant. This stock may have a total sulfur content of1.2% and at the same time have the approximate boiling range for motorfuel. However, it may not be distillable without decomposition of thesulfur compounds to an extent which gives a percentage of sulfur in theoverhead product greatly in excess of that allowed in commercialgasoline.

The gasoline stock may be treated with about 1% by volume of 89%phosphoric acid at a temperature of 50 C. The run may be made bytreating successive.20% portions of the oil with the same acid, thismethod of operationsimulating counterfiow treatment. The sulfur contentof the combined oil' portions may be less than 0.05% and, afterseparation from the phosphoric acid sludge, it may be distilled toproduce a water white color and gum stable gasoline suitable formarketing. The 1% by volume of phosphoric acid used corresponds to theuse of about 6 pounds of acid per barrel of stock treated which is areasonable and practical figure when considered from an economicstandpoint. When using sulfuric acid of commercial grade in treatingcracked distillates or other hydrocarbon products five pounds per barrelis considered a very mild treatment.

A further yield of gasoline is recoverable by treating the phosphoricacid sludge with steam and also an amount of isopropyl' alcoholapproximately equivalent to the sulfuric acid esters corresponding tothe 1 .20 sulfur content, the alcohol being obtained by neutralizing andagain distilling the sludge. i

The present process thus appears as a valuable adjunct to syntheticprocesses in which olefins are polymerized in the presence of sulfuricacid catalysts.

The foregoing specification and example will serve their respectivepurposes of developing the character of the invention in showing itscommercial value. but neither is to be considered as imposing unduelimitations upon its generally broad scope.

I claim as my invention:

1. In the synthesis of liquid hydrocarbons by I polymerization of olefingases in the presence of esters from the synthesized hydrocarbon liquidwhich comprises treating the latter with phosphoric acid.

2. In the synthesis of liquid hydrocarbons by polymerization of olefingases in the presence of sulphuric acid as a polymerizing agent andwherein there are formed sulphuric acid esters which are soluble in thesynthesized liquid, the method of removing such dissolved sulphuric acidesters from the synthesized hydrocarbon liquid which comprises treatingthe latter with a mixture of phosphoric and sulphuric acids;

3. In the synthesis of liquid hydrocarbons by polymerization of olefingases in the presence of sulphuric acid as a polymerizing agent andwherein there are formed sulphuric acid esters which are soluble in thesynthesized liquid, the

method of removing such dissolved sulphuric acid esters from thesynthesized hydrocarbon liquid which comprises treating the latter withphosphoric acid at a temperature of from about 50 C. to 60 C.

4. In the synthesis of liquid hydrocarbons by polymerization of olefingases in the presence of sulphuric acid as a polymerizing agent andwherein there are formed sulphuric acid esters which are soluble in thesynthesized liquid, the method which comprises converting such dissolvedsulphuric acid esters into phosphoric acid esters by treating thesynthesized hydrocarbon liquid with phosphoric acid, separating thehydrocarbon liquid from the resultant phosphoric acid sludge containingthe phosphoric acid esters, hydrolyzing the latter to form phosphoricacid and alcohol, and recycling the thus regenerated phosphoric acid tothe process for treatment of additional quantites of the synthesizedhydrocarbon liquid.

VLADIMIR IPATIEFF.

